Fatty liver is a condition where fat builds up in liver cells, and is a morbid condition where fat medically exceeds 5% or more of the total liver weight. Liver diseases including fatty liver have been reported to be among the most severe diseases after cancer among causes of death of the population of adults in their 40s to 50s in developed countries. 30% of the population of major countries including developed countries show fatty liver symptoms, 20% of these cases progress to cirrhosis, and about half of patients with cirrhosis die of liver disease within 10 years after the diagnosis.
Fatty liver may be divided into alcoholic fatty liver disease and nonalcoholic fatty liver disease (NAFLD) due to obesity, diabetes, hyperlipidemia, drugs, and the like.
Nonalcoholic fatty liver disease is simple fatty liver which does not accompany an inflammatory response from patients who do not intake excessive amounts of alcohol, and a wide range of diseases that progress therefrom including an inflammatory response of liver cells, liver fibrosis, and cirrhosis. Nonalcoholic fatty liver disease is divided into primary and secondary nonalcoholic fatty liver disease according to the cause thereof, and it is known that primary nonalcoholic fatty liver disease occurs due to hyperlipidemia, diabetes, obesity, or the like, which is a characteristic of metabolic syndromes, and secondary nonalcoholic fatty liver disease occurs due to nutritional causes (a rapid decrease in body weight, starvation, and enteric bypass), various drugs, toxic substances (poisonous mushrooms and bacterial toxins), metabolic causes, and other factors. It is known that nonalcoholic fatty liver disease is associated with diabetes and obesity which are important characteristics of metabolic syndromes which are a primary factor in about 50% of patients with diabetes, about 76% of patients with obesity, and almost of the patients with diabetes accompanying obesity. Further, as a result of performing biopsies on patients with diabetes and obesity in which the levels of alanine aminotransferase (ALT) were increased, the incidence of steatohepatitis was 18 to 36%.
Meanwhile, the therapeutic effects of administration of several diabetes or obesity therapeutic drugs on fatty liver disease are known, and there are reports that, among these therapeutic drugs, orlistat that has been used as an oral obesity therapeutic agent improves restoration of liver tissue in patients with steatohepatitis. In addition, there are reports that metformin reduces serum liver enzyme levels and necrotizing inflammation and fibrosis of the liver in patients with nonalcoholic fatty liver which does not accompany diabetes, as well as reports that a thiazolidinedione (TZD)-based drug that is an agonist of a peroxisome proliferator-activated receptor (PPAR) suppresses fat accumulation in the liver and muscles, and exhibits a direct anti-fibrosis action on the liver in animal models of nonalcoholic fatty liver disease. However, despite the development of these therapeutic drugs (Korean Patent Application Laid-Open No. 10-2013-0103190), drugs useful for the treatment of fatty liver disease are insufficient and there is no established therapeutic method for fatty liver disease, and thus the only recommendations that can be made are appropriate exercise and diet.